1. Field of the Invention
The present invention relates to a flat type refrigerating open showcase whose top surface is open and, more particularly, to a technology for forming an air curtain therefor.
2. Description of the Related Art
A conventional refrigerating open showcase of this type will be described with reference to FIG. 9. FIG. 9 is a sectional view of a conventional refrigerating open showcase.
As shown in FIG. 9, a refrigerating open showcase 1 includes a heat insulating showcase body 2 whose top surface is open, an inner plate 3 erecting along a side wall 2a of the showcase body 2, and a bottom plate 4 for closing the lower part of the inner plate 3. The upper end of the side wall 2a of the showcase body 2 projects to the inside. The upper end of the inner plate 3 is positioned under a projecting portion 2b of the side wall 2a. Thereby, an air passage 5 is formed by a gap between the side wall 2a of the showcase body 2 and the inner plate 3 and a gap between a bottom plate 2c of the showcase body 2 and the bottom plate 4. In the air passage 5, a cooler 6 and a fan 7 are provided. On the discharge port 8 side of the air passage 5, a straightening element 9 is disposed.
With this construction, when the cooler 6 and the fan 7 are operated, cold air having been cooled by the cooler 6 is discharged through a discharge port 8, and the cold air is sucked through a suction port 10. Thus, what is called an air curtain is formed over a range from the discharge port 8 to the suction port 10 on the top surface of the showcase body 2. Thereby, commodities stored in a commodity storage portion 11 can be cooled.
In the above-described conventional refrigerating open showcase, as shown in an enlarged view of FIG. 10, the upper end of the inner plate 3 on the suction port 10 side is bent toward the commodity storage portion 11. Also, as a conventional refrigerating open showcase 1 of another type, a refrigerating open showcase in which the upper end of the inner plate 3 on the suction port 10 side is bent toward the side wall 2a of the showcase body 2, as shown in an enlarged view of FIG. 11, is known. Both of these bent portions 3e are provided to increase the strength of the inner plate 3. In the above-described refrigerating open showcase 1, however, since the flow velocity of cold air in the vicinity of the suction port 10 is lower than that in the vicinity of the discharge port 8, the commodities stored near the suction port 10 are sometimes cooled insufficiently. Also, commodities sometimes drop into the air passage 5 through the suction port 10.
As a conventional refrigerating open showcase 1 of still another type, a refrigerating open showcase in which a guard 12 for preventing commodities from dropping is provided in a range from the projecting portion 2b of the side wall 2a to the air passage 5, as shown in FIG. 12(A), is known. In the guard 12, vent holes 12a are formed by punching as shown in FIG. 12(B). On the air passage 5 side of the guard 12, heaters 13 for preventing frosting are provided. However, such a refrigerating open showcase 1 has a problem of increased cost because it requires the guard 12 and the heater 13. Also, it has a problem of increased power consumption caused by the driving of the heater 13.
As a refrigerating open showcase of a type similar to the refrigerating open showcase 1 shown in FIG. 12, a refrigerating open showcase in which the upper part of the inner plate 3 is bent slantwise and the upper end thereof is attached to the side wall 2a, and vent holes 3d are formed in the inclined portion, as shown in FIG. 13, is known. On the back side of the inclined portion, the heaters 13 for preventing frosting are provided. Although such a refrigerating open showcase 1 has an advantage that the number of parts decreases as compared with the refrigerating open showcase shown in FIG. 12, it still has a problem of increased power consumption caused by the driving of the heater 13.
In the conventional refrigerating open showcase 1, as shown in an enlarged view of an essential portion of FIG. 14, the upper end of the inner plate 3 on the discharge port 8 side is bent substantially horizontally toward the commodity storage portion 11. Also, the straightening element 9 disposed in the discharge port 8 is made up of a plurality of straightening vanes 9a to 9c which are formed along the air passage 5 and arranged at predetermined intervals. The intervals of the straightening vanes 9a to 9c are adjusted so that the flow velocities of cold air discharged from between the straightening vanes 9a to 9c differ from each other. Specifically, the intervals are adjusted so that the flow velocity increases from the upper layer toward the lower layer. In FIG. 14, the flow velocity and direction of each layer are indicated by the length and direction of an arrow mark. In such a construction, however, since the flow velocity of the lowermost layer which is closest to the commodities stored in the commodity storage portion 11 is highest, cold air of this lowermost layer hits the commodities, and hence there is a fear that great turbulence occurs in the air curtain. Therefore, there may arise a problem in that the outside air intrudes into the commodity storage portion 11, which decreases the cooling efficiency.